San Diego-based MDA DataQuick said 19,528 homes sold last month in the six-county area, up from 16,208 in October but down 12.5 percent from 22,328 in the year-ago period.

Sales have increased an average of 12.9 percent since DataQuick began compiling statistics in 1988, the firm said.

Rich Cosner, who owns a real estate brokerage that does business in Riverside, San Bernardino and Orange counties, said buyers seemed to have been spurred into action by rising mortgage interest rates.

"Rates rising just a little bit got a lot of people off the fence," Cosner said. "The fear is that it may get more expensive later in the year."

The region's median home price increased 0.3 percent to $290,000 last month from $289,000 in December 2009 and grew 1 percent from $287,000 in November, DataQuick said.

The firm said the sluggish job market and limited access to credit were keeping the median from appreciating much over the previous year's prices.

John Husing, an economist with San Bernardino County-based Economics & Politics Inc., said he was encouraged to see prices remain above their recession-era lows, indicating a sustained recovery.

"The fact is you've had enough demand in order to offset supply that is being released," he said. "The market continues to hold its own on the price side."

The median was also being tugged down by weak sales of new homes, which reached their lowest level for a December since DataQuick began keeping records.

"It's hard to ignore the ongoing slump in the Southland's new-home market," DataQuick president John Walsh said. "What happens next will hinge largely on the pace of the economic recovery and the manner in which lenders manage their inventories of distressed properties, which are competition for new homes."

DataQuick said 21.1 percent of last month's sales were for homes costing more than $500,000, the same as November but up from 20.7 percent in December last year. Over the last decade, an average of 26.9 percent of all December home sales were for more than $500,000.

Cosner said high-end properties traditionally sell to move-up buyers, who use equity in their current homes to buy more expensive ones. But he said such buyers are scarce these days.

"You've got a very robust first-time home market and then you've got people buying foreclosures and short sales, but what we're missing is the move-up market and that won't happen until people have equity again," he said.

Foreclosures accounted for 34.3 percent of resales last month, down from 35.2 percent in November and 39.6 percent a year ago.